1. Field of the Invention
The invention disclosure concerns a modularly magnetic resonance (MR) transmission system with a number of essentially similar PCI-TX modules, of which one is a “master module” and the others are “slave modules”.
2. Description of the Prior Art
The following abbreviations and terms are used in the subsequent explanations:                Mod: modulator        RX: receiver        TX: transmit or transmit path        GPA: gradient power amplifier        SPA: shim power amplifier        RFPA: RF power amplifier        MRIR: MR image reconstruction=image computer        AMC: advanced measurement control=control computer with PCI-TX card        TALES: transmit antenna level sensor=RF volt meter for measurement of the transmission power        PCI: peripheral component interconnect=a bus standard that is used for, among other things, such TX modules        Synth: synthesizer        RFSWD: RF safety watch dog        SAR: specific absorption rate        NCO: numerical controlled oscillator        RX1 to RX4: receiver cassettes 1 through 4        
An MR system conventionally has the following TX (transmit) channels:
One RF transmission channel that is very fast and can be controlled/modified in a μsec clock pulse in terms of amplitude and phase and, to a limited degree, also in terms of the frequency. The RF values are varied during the measurement.
Three gradient channels (Gx, Gy, Gz) that are very fast and can be controlled/modified in a μsec clock pulse in terms of amplitude and phase as well as in terms of the frequency. The gradient values are varied during the measurement.
Five shim channels (typically of the 2nd order) that are very slow and are typically altered only before and after an MR measurement.